Flow responsive transmitter and indicator

ABSTRACT

In the measurement of fluid flow, the generation of a linearly varying signal and a pulsation free display are provided by a flow responsive indicator having digit displays for numerically indicating the rate of measured flow. The digit displays are driven in accordance with a measured flow signal applied to circuitry for generating an updated display signal from a previous display signal and the current value of the measured flow signal. This analog updated display signal is converted into a digital signal for driving circuitry connected to each of the digit displays. The measured flow signal applied to the indicator is generated at a flow transmitter including a transducer, such as a Hall effect element. This transducer generates a signal varying with flow in response to movement of a vane mounted in proximity thereto. To provide a signal varying linearly with flow rate, a flexible element extends into the fluid stream and by action thereof displaces the vane with reference to the transducer to generate the desired linearly varying signal.

This is a division of application Ser. No. 5,830, filed Jan. 21, 1987,now U.S. Pat. No. 4,898,036.

TECHNICAL FIELD

This invention relates to the measurement and display indication of afluid flow, and more particularly, to the measurement and displayindication of turbulent and pulsating fluid flow.

BACKGROUND ART

Heretofore, it has been recognized that in the measurement of fluidflow, laminar flow conditions are preferred to achieve more accurateflow measurement. It has also long been recognized that a continuingproblem in measurement of fluid flow is establishing a linearrelationship between the measured flow and a signal varying with theflow. Various techniques have been employed to create laminar flow in aturbulent flow condition and to linearize the relationship between asignal varying with measured flow and the rate of flow passing atransducer. The various techniques heretofore used in the measurement ofthe rate of flow of a fluid have been acceptable so long as the flowconditions are reasonably well defined.

Where the conditions of the fluid flow to be measured are not welldefined, there has developed a need for a transmitter and a flowindicator that has an acceptable accuracy factor. An example of a fluidsystem wherein the flow cannot be well defined and includes pulsatingflow conditions are vehicle mounted systems. For example, a fluid systemmounted on a truck chasis by necessity results in only a few very shortstraight runs of pipe that have been defined as the most desirablelocation for a fluid flow transducer. Thus, fluid systems on a vehiclechasis usually require the measurement of flow in a turbulent flowcondition. Furthermore, the fluid discharge of such vehicle mountedsystems is also pulsating which compounds the problem of producing anaccurate flow measurement.

When measuring flow in a large fixed installation, with a reasonablylong productive life, the cost of the fluid measuring transducer andindicator is usually not considered to be a significant part of thetotal system cost. However, when measuring fluid flow in a vehiclemounted system, which may have only a relatively short productive lifespan, the cost of the fluid flow measuring transducer and indicatorbecomes a more significant factor. Thus, while some of the previouslyused techniques for measurement of flow are available for the vehiclemounted system, the cost of such techniques are prohibitive and out ofproportion to the overall cost of the system. Any fluid flow measuringsystem for a vehicle mounted flow system requires a careful analysis ofthe costs involved.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a flowresponsive indicator including means for generating a signal varyingwith a measured flow. This flow signal along with a previously generateddisplay signal are input to a means for combining that is part of ameans for generating an updated display signal. Thus, the updateddisplay signal is generated from a combination of a previously generateddisplay signal and the flow signal. At timed intervals, a controllerconnects in sequence the previous display signal to the means forcombining, the flow signal to the means to combining, and the updateddisplay signal to a flow display indicator thereby providing a digitaldisplay of the measured flow.

Further, in accordance with the present invention, the means forgenerating the updated display signal includes a first means for storingthe previous display signal, a second means for storing the flow signaleach connected to the means for combining the stored previous displaysignal with the stored flow signal to generate the updated displaysignal.

Also in accordance with the present invention there is provided a flowresponsive transmitter having a housing within which is mounted a vanepositionable in response to the rate of flow in a fluid flow stream.Mounted within the housing is a transducer responsive to movement of thevane to generate a measured flow signal to a flow responsive indicator.Connected to the vane and extending into the flow stream is a flexibleelement that tends to smooth out turbulent flow and positions the vanewith reference to the transducer to cause the measured flow signal tovary linearly with the rate of flow. In a preferred embodiment theflexible element connected to the vane comprises a tightly coiled springhaving the necessary characteristics to move the vane with reference tothe transducer to cause the measured flow signal to vary linearly.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following detaileddescription taken in conjunction with the accompanying drawings.

Referring to the drawings:

FIG. 1 is a pictorial view of a flow responsive digital indicatorexploded to show circuit boards supporting the necessary electronicelements to respond to a flow measurement signal and driving digitalindicators;

FIG. 2 is a schematic diagram of one of three circuit boards of FIG. 1for responding to a flow measurement signal;

FIG. 3 is a schematic diagram of a second of the three circuit of boardsof FIG. 1 for conversion of the output of the circuit of FIG. 2 intodigital display drive signals;

FIG. 4 is a schematic diagram of the third circuit board of FIG. 1having the digital display elements responding to the drive signals forthe circuit of FIG. 3;

FIG. 5 is a pictorial view of a flow responsive transmitter, partiallyexploded, for generating a signal representing flow measurement;

FIG. 6 is a detailed illustration of the vane and transducer for theflow responsive transmitter of the FIG. 5; and

FIG. 7 is a schematic diagram of a circuit responding to the output ofthe transducer of FIG. 6 and generating a signal varying linearly withflow to be applied to the circuitry of FIG. 2.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown the flow responsive indicator of thepresent invention including a housing 10 and a front panel 12 having aviewing window 14 in which appears a four digit display for numericallyindicating the rate of flow of a measured fluid. The digital displays16, 18, 20 and 22 are shown mounted on a circuit board 24, one of threecircuit boards that support the circuitry for driving the digitaldisplays in accordance with an applied signal representing measuredflow. Also illustrated is a circuit board 26 that contains circuitcomponents that respond to the signal representing measured flow andgenerating at timed intervals an updated display signal applied to acircuit board 28. The circuit board 28 contains circuit componentsresponding to the updated display signal for converting these signalsinto a digital format for driving the circuitry of the circuit board 24.The circuit boards 24, 26 and 28 are assembled in a parallel arrangementinto the housing 10 such that the displays 16, 18, 20 and 22 arepositioned in the viewing window 14.

Referring to FIG. 2, there is schematically shown the circuitry of thecircuit board 26 including an amplifier 30 having an input line 32connected to receive a signal varying with measured flow from a flowtransmitter such as illustrated in FIG. 5, to be described. Theamplifier 30 is part of a circuit responding to the flow signal togenerate an updated display signal. Also included in the circuit of FIG.2 is an amplifier 34 receiving an input signal from a zero adjustingnetwork mounted on the circuit board 24 and schematically illustrated inFIG. 4, to be described. Output signals from the amplifiers 30 and 34are applied through resistors 36 and 38, respectively, to be summed atthe input terminal of an amplifier 40. Thus, the output of the amplifier40 varies with the signal representing measured flow applied to theamplifier 30 and adjusted for zero flow rate at the output of theamplifier 34.

An output of the amplifier 40 is applied to an amplifier 42 generatingan output applied through a diode 44 to a filter network comprising aresistor 46 in parallel with a capacitor 48 The output of the filternetwork is applied to one input of an amplifier 50 as part of a sampleand hold circuit consisting of a diode 52 and a storage capacitor 54. Avoltage appearing across the capacitor 54 is a flow signal varying withlinearly measured flow.

At timed intervals controlled by a sequence controller 56, the flowsignal across the capacitor 54 is applied to a storage capacitor 58through an amplifier 60. Specifically, the output of the amplifier 60 isapplied through a switch 62 as part of the sequence controller 56. Thus,by operation of the switch 62, the flow signal across the capacitor 54is transferred to and stored across the capacitor 58. This flow signal,appearing as a voltage across the capacitor 58, is applied to one inputof an amplifier 64 as part of a circuit for generating an updateddisplay signal to an analog-to-digital converter of the circuit board28. Also included as a part of the circuit for generating the updateddisplay signal is an amplifier 66 having an input connected to a storagecapacitor 68 that receives at timed intervals, through the sequencecontroller 56 the previously generated updated display signal. Thestorage capacitor 68 is charged through a switch 70 as part of thesequence controller 56.

Output signals from the amplifiers 64 and 66 are applied throughresistors 72 and 74, respectively, to one input of an amplifier 76. Byoperation of the amplifiers 64 and 66 and the resistors 72 and 74, alongwith the amplifier 76, the flow signal stored across the capacitor 58and the previous display signal stored across the capacitor 68 aresummed into the updated display signal on a line 78 from the amplifier76.

The output of the amplifier 76, as the updated display signal is appliedto a range adjust network on the circuit board 24 and will be describedwith reference to FIG. 4. The range adjusted signal from the circuitboard 24 is applied to the sequence controller 56 on a line 80 and attimed intervals is applied to a line 82 by means of a switch 84 as partof the sequence controller.

In operation, the circuit of FIG. 2 responds to a signal varying withmeasured flow and generates an updated display signal on the line 82.Sequence signals are applied to lines 86 to operate the switches of thesequence controller 56 including a switch 88 connected to the storagecapacitor 54. At sequence clock zero, a clock pulse actuates the switch70 into a closed position to apply the previously updated display signalto the storage capacitor 68. At the termination of this clock pulse, theswitch 70 is opened and following a preset time interval, a clock pulseis applied to the sequence controller 56 to close the switch 88. Thisdischarges the flow signal stored across the storage capacitor 54 tozero and after a preset time interval the switch 88 reopens and the flowsignal again builds up across the storage capacitor 54. Note, the flowsignal now stored across the capacitor 54 is the most current value ofthe signal applied to the amplifier 30 that varies with measured flow.At a timed interval after opening the switch 88, a sequence clock pulseis applied to the controller 56 closing the switch 62 to apply the mostcurrent value of the flow signal across the capacitor 54 to the storagecapacitor 58. Upon timing out of this third sequence clock pulse, theswitch 62 is opened and at this point in the sequence both thecapacitors 58 and 68 have current stored signal values. These currentvalues are then summed to generate the updated display signal on theline 78, which after range adjustment, is re-routed to the circuit ofFIG. 2 on the line 80. At a preset time interval later, the switch 84 isclosed and the updated display signal is applied by means of the line 82to the analog-to-digital circuit on the circuit board 28. Included as apart of the circuit on the board 28 is the clock pulse generator to bedescribed.

The circuitry of FIG. 2 also includes a regulated power supply 90 ofconventional design consisting of interconnected diodes, resistors,capacitors and resistor elements. Further description of this powersupply is not considered to benefit an understanding of the invention.

The output of the power supply 90 is generated on a line 92 and providesa regulated voltage to various components on the circuit boards 24, 26and 28 including those circuit elements most recently described forgenerating an updated display signal. Also illustrated as part of thepower supply 90 is a line 94 that functions as circuit ground forvarious components of the circuit boards 24, 26 and 28.

In addition to the circuit components previously described, theregulated voltage on the line 92 is applied to an amplifier 96 thatreceives a second input from the output of the amplifier 76, that is,the updated display signal. The output of the power supply 90 is appliedto the amplifier 96 through an input resistor 98 and is identified as ananalog ground for the various components of the circuits of the boards24, 26 and 28. An output of the amplifier 96 is applied to the sequencecontroller 56 for controlling the operation of the switch 84. The switch84 is also controlled from a test switch as part of the circuit board24, to be described.

The analog ground at the input of the amplifier 96 is also applied to aninput of an amplifier 100 having a second input from the power supply90. Amplifier 100 generates an offset analog ground signal. This offsetground is applied to the circuit components of the circuit board 28.

To complete the description of the circuit of FIG. 2, an amplifier 102is connected to the power supply 90 for generating a reference DCvoltage applied to the analog to digital converter of the circuit board28.

Referring to FIG. 3, there is shown a schematic diagram of circuitryresponsive to the updated display signal on the line 82 from thesequence controller 56. An updated display signal on the line 82 isapplied to an analog-to-digital converter 104 at the terminal V_(x).Also connected to the line 82 is a input resistor 106 tied to analogground at the output of the amplifier 100. A drive voltage for theanalog-to-digital converter 104 is applied on line 92 from the regulatedsupply 90.

The analog-to-digital converter 104 receives the updated display signalon line 82 at timed intervals as determined by a sequence clock pulseprovided on a line 108 at an output of a sequence clock 110. Thesequence clock 110 also provides the sequence clock pulses to thesequence controller 56 over the lines 86. Operation of theanalog-to-digital converter is clocked by an output of the sequenceclock 110 on a line 112.

An output of the analog-to-digital converter 104 is a digitalrepresentation of the updated display signal generated in the circuitryof FIG. 2. This digital signal is generated an output lines 114 that areindividually applied to either an amplifier network 116a or an amplifiernetwork 116b. The function of the amplifier networks 116a and 116b is toamplify the level of the digital signal from the analog-to-digitalconverter 104 to drive display circuitry to be described. Each of thenetworks 116a and 116b consists of a buffer amplifier for each of theoutput lines of the analog-to-digital converter 104. These bufferamplifiers have outputs connected individually to one of an array oflatch circuits 118, 120, 122 and 124. Also, the binary code from theanalog-to-digital converter 104 on the lines 114a, 114b, 114c and 114dare applied through buffer amplifiers of the network 116b to drive allof the latch circuits, 118, 120, 122 and 124. The output of theindividual latch circuits is a binary code for driving a digit displayas illustrated in FIG. 4.

Referring to FIG. 4, there is shown digit displays, 126, 128, 130 and132 and associated drive circuitry. This drive circuitry includesdecoder drivers 136, 138, 140 and 142 for each of the digit displays.The driver decoder 138 is connected to the latch circuit 118, the driverdecoder 138 connects to the latch circuit 120, the driver decoder 140connected to the latch circuit 122 and the driver decoder 142 connectsto the latch circuit 124. Also connected to each of the driver decodersand the digit displays are various circuit elements for driving each ofthe displays to produce a numerical indication of the flow signal inputto the amplifier 30 of FIG. 2.

Also shown in FIG. 4, which is the circuit board 24 of FIG. 1, is a zeroadjust network including a potentiometer 144 in series with a resistor146 with the center tap of the potentiometer connected to the input ofthe amplifier 34 of FIG. 2. Also shown in FIG. 4 is a test pushbutton148 for turning on a transistor 150 to test the digit displays 126, 128,130 and 132. There is further included in FIG. 4 a flow, or range,adjust potentiometer 152 in series with resistors 154 and 156. Thisnetwork is connected to the lines 78, 80 and 81 of FIG. 2.

The circuitry of FIGS. 2 through 4 responds to a signal varying withmeasured flow to provide a digital display in the instrument illustratedin FIG. 1. The measured flow signal is sampled and stored andsubsequently combined with a previous display signal to generate anupdated display signal. At timed intervals, the sequence controllersequences the operation of the circuit producing a stabilized updateddisplay signal in an analog format that is converted into a digitalsignal by an analog-to-digital converter. The digital representation ofthe updated display signal drives a four digit display to numericallyindicate a rate of flow as represented by the signal varying withmeasured flow. By operation of the display as described, oscillatingflow signals as caused by turbulent flow are smoothed out thus providinga more steady numerical display.

Referring to FIGS. 5 and 6, there is shown a pictorial illustration of aflow transmitter for generating a signal varying with measured flow tobe applied to the amplifier 30 of FIG. 2. This measured flow signal isgenerated by a Hall effect transducer 160 mounted in a housing 162 thatalso supports a movable vane 164. The vane 164 is pivoted to the housing162 on a pivot shaft 166 and extends from the housing through adiaphragm seal 168. Within the housing 162, the vane 164 terminates atthe transducer 160 and is movable with reference thereto. Mounted to thevane 164 is a magnet (not shown) that cooperates with the transducer160, such as a Hall effect element, to generate a signal on output linesvarying with the rate of flow of a measured fluid.

It is well known that a signal generated in accordance with rate of flowby the mechanism so far described will be non-linear and some provisionmust be made to linearize the signal. Connected to the extension of thevane 164 from the housing 162 is a flexible element 174 in the shape ofa tightly wound coil spring. This element extends into the fluid flowand imparts a motion to the vane 164 relative to the transducer 160 toproduce a linear flow signal on the output lines. Further, theflexibility of the element 174 tends to smooth out the turbulent flow,such as found in vehicle mounted fluid flow systems. In operation, asthe flow past the flexible element increases, the spring assumes anincreasing bending profile, and it is this characteristic of the element174 that provides the linearizing action for the signal on the outputlines. Compared with electronic linearization, the tightly wound springprovides an economical and reliable linearization technique.

The housing 162 is enclosed within a case 176 having an uppercylindrical shaped portion 176a and a lower shroud 176b. The shroud 176bis provided with a passage in line with the fluid flow to balance theforces on the diaphragm 168 as the element 174 extends into the fluidpath.

Mounted to the upper section 176a is a circuit amplifier 177 thatreceives the output of the transducer 160 and amplifies it fortransmission to the circuit board 28 of FIG. 2 as received by theamplifier 30.

To complete the transmitter of FIG. 5, a cap or cover 178 is fitted overthe upper part of the case 176 and includes the connecting lines 180attached to the circuit board 28 of FIG. 2.

Referring to FIG. 7, there is shown a schematic of the amplifier 177 forthe flow indicator transmitter of FIGS. 5 and 6. The transducer 160,which as mentioned may be a Hall effect element, provides an outputvarying with movement of the vane 164 to the input of a gain amplifier190 through a divider network consisting of resistors 192 and 194. Thegain of the amplifier 190 is adjusted by means of a potentiometer 196and the output is applied to one input of a differiential amplifier 198.A second input to the amplifier 198 is the output of a compensatingcircuit including an amplifier 200. The compensating circuit isconnected to a zero adjust network including a thermistor circuit 202 inseries with a potentiometer 204 and resistors 206 and 208.

An output of the amplifier 198, which is a signal varying with rate offlow and compensated by the output of amplifier 200, is applied to adriver amplifier 210 which drives an Darlington pair 212 as the outputdriver of the flow indicator transmitter of FIG. 7. Thus, in operation,as the rate of flow past the flexible element 174 varies the position ofthe vane 164 with reference to the transducer 160 causes the output ofthe transducer to vary linearly with the flow rate. This linearrelationship between the output of the transducer 160 and the flow rateis the result of the flexible element 174 imparting a non-linear motionto the vane 164. This output of the transducer 160 is amplified by thecircuit of FIG. 7 to produce a signal on a line 214 that varies withmeasured flow. This signal on the line 214 is applied to the input ofthe amplifier 30 of the circuit board 28 of FIG. 2.

Although the invention has been described and illustrated in detail, itis to be understood that the same is by way of illustration and exampleonly, and is not to be taken by way of limitation. The spirit and scopeof this invention are to be limited only by the terms of the appendedclaims.

I claim:
 1. A flow responsive transmitter, comprising:a housing havingan internal cavity; first means mounted in the cavity of said housingand extending therefrom into a flow stream, said first means including avane at one end and a spring as an integral unit with said vaneextending into the flow stream to flex in response to the flow streamand position said vane linearly with reference to the flow stream andeffect a dampening of turbulent flow motion; flexible sealing meansconnected to said first means and said housing to seal the cavity fromthe flow stream; and a transducer mounted in said housing and responsiveto the movement of said vane to generate a signal varying with measuredflow, the movement of said vane with reference to said transducerprovides a measured flow signal varying linearly with the rate of flow.2. A flow responsive transmitter as set forth in claim 1 including anamplifier responsive to the signal varying with measured flow and havingan output for transmission to a flow responsive indicator.
 3. A flowresponsive transmitter as set forth in claim 1 wherein said transducerincludes a Hall effect element responsive to movement of said vane togenerate the signal varying with measured flow.